1GRDINFO(1) GMT GRDINFO(1)
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6 grdinfo - Extract information from grids
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9 grdinfo grdfiles [ -C ] [ -D[xoff[/yoff][+n] ] [ -F ] [
10 -I[dx[/dy]|b|i|r] ] [ -L[0|1|2|p|a] ] [ -M ] [ -Rregion ] [
11 -T[dz][+a[alpha]][+s] ] [ -V[level] ] [ -fflags ]
12 Note: No space is allowed between the option flag and the associated
14 arguments.
15
17 grdinfo reads a 2-D binary grid file and reports metadata and various
18 statistics for the (x,y,z) data in the grid file(s). The output infor‐
19 mation contains the minimum/maximum values for x, y, and z, where the
20 min/max of z occur, the x- and y-increments, and the number of x and y
21 nodes, and [optionally] the mean, standard deviation, and/or the
22 median, median absolute deviation of z, and/or the mode (LMS), LMS
23 scale of z, and number of nodes set to NaN. We also report if the grid
24 is pixel- or gridline-registered and if it is a Cartesian or Geographic
25 data set (based on metadata in the file).
26
28 grdfile
29 The name of one or several 2-D grid files. (See GRID FILE FOR‐
30 MATS below.)
31
33 -C Formats the report using tab-separated fields on a single line.
34 The output is w e s n z0 z1 dx dy nx ny[ x0 y0 x1 y1 ] [ med
35 scale ] [mean std rms] [n_nan]. The data in brackets are output
36 only if the corresponding options -M, -L1, -L2, and -M are used,
37 respectively. If the -I option is used, the output format is
38 instead NF w e s n z0 z1, where NF is the total number of grids
39 read and w e s n are rounded off (see -I).
40 -D[xoff[/yoff][+i]
42 Divide a single grid's domain (or the -R domain, if no grid
43 given) into tiles of size dx times dy (set via -I). You can
44 specify overlap between tiles by appending xoff[/yoff]. If the
45 single grid is given you may use the modifier +i to ignore tiles
46 that have no data within each tile subregion.
47 -F Report grid domain and x/y-increments in world mapping format
49 [Default is generic]. Does not apply to the -C option.
50 -I[dx[/dy]|b|i|r]
52 Report the min/max of the region to the nearest multiple of dx
53 and dy, and output this in the form -Rw/e/s/n (unless -C is
54 set). To report the actual grid region, select -Ir. For a grid
55 produced by the img supplement (a Cartesian Mercator grid), the
56 exact geographic region is given with -Ii (if not found then we
57 return the actual grid region instead). If no argument is given
58 then we report the grid increment in the form -Ixinc/yinc. If
59 -Ib is given we write each grid's bounding box polygon instead.
60 -L[0|1|2|p|a]
62 -L0 Report range of z after actually scanning the data, not
64 just reporting what the header says.
65 -L1 Report median and L1 scale of z (L1 scale = 1.4826 *
67 Median Absolute Deviation (MAD)).
68 -L2 Report mean, standard deviation, and root-mean-square
70 (rms) of z.
71 -Lp Report mode (LMS) and LMS scale of z.
73 -La All of the above.
75 Note: If the grid is geographic then each node represents a
77 physical area that decreases with increasing latitude. We
78 therefore report spherically weighted statistical estimates for
79 such grids.
80 -M Find and report the location of min/max z-values, and count and
82 report the number of nodes set to NaN, if any.
83 -Rxmin/xmax/ymin/ymax[+r][+uunit] (more ...)
85 Specify the region of interest. Using the -R option will select
86 a subsection of the input grid(s). If this subsection exceeds
87 the boundaries of the grid, only the common region will be
88 extracted.
89 -T[dz][+a[alpha]][+s]
91 Determine min and max z-value. If dz is provided then we first
92 round these values off to multiples of dz. To exclude the two
93 tails of the distribution when determining the min and max you
94 can add +a to set the alpha value (in percent [2]): We then sort
95 the grid, exclude the data in the 0.5*alpha and 100 - 0.5*alpha
96 tails, and revise the min and max. To force a symmetrical range
97 about zero, using minus/plus the max absolute value of the two
98 extremes, append +s. We report the result via the text string
99 -Tzmin/zmax or -Tzmin/zmax/dz (if dz was given) as expected by
100 makecpt.
101 -V[level] (more ...)
103 Select verbosity level [c].
104 -f[i|o]colinfo (more ...)
106 Specify data types of input and/or output columns.
107 -^ or just -
109 Print a short message about the syntax of the command, then
110 exits (NOTE: on Windows just use -).
111 -+ or just +
113 Print an extensive usage (help) message, including the explana‐
114 tion of any module-specific option (but not the GMT common
115 options), then exits.
116 -? or no arguments
118 Print a complete usage (help) message, including the explanation
119 of all options, then exits.
120
122 By default GMT writes out grid as single precision floats in a
123 COARDS-complaint netCDF file format. However, GMT is able to produce
124 grid files in many other commonly used grid file formats and also
125 facilitates so called "packing" of grids, writing out floating point
126 data as 1- or 2-byte integers. (more ...)
127
129 To obtain all the information about the data set in file
130 hawaii_topo.nc:
131 gmt grdinfo -L1 -L2 -M hawaii_topo.nc
133
135 gmt, grd2cpt, grd2xyz, grdedit
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138 2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
1395.4.5 Feb 24, 2019 GRDINFO(1)